The present invention relates to a dual-circuit pressure control valve having a change-over point adjustable from the outside for use in hydraulic dual-circuit brake systems of automotive vehicles. The pressure control valve includes two cylinders each connected to one of the two brake circuits arranged parallel to each other in a housing and containing therein control pistons whose actuating tappets project outwardly on the same end face of the cylinders and are directly acted upon by a common control lever. The control lever may be subjected to a control force and is supported at the housing tiltably around a transverse axis, which runs perpendicular relative to the cylinder axes, and around its longitudinal axis, with means being provided for an even distribution of the control force onto the two control pistons and with stop means being provided between the control lever and components which are fastened to the housing, which stop means limit the tilting movement of the lever around its longitudinal axis without inhibiting the tilting movement around its transverse axis as described in copending U.S. patent application of B. Schopper and P. Tandler, Ser. No. 160,523 filed June 18, 1980, now U.S. Pat. No. 4,332,423, issued June 1, 1982, assigned to the same assignee as the instant application.
The above-cited copending application describes a dual-circuit pressure control valve, which safeguards an even distribution of the control force onto both control pistons without any complicated force transmission elements in a simple, yet reliable manner. In a preferred embodiment of the known dual-circuit pressure control valve, stop means are provided between the lever and components fastened to the housing which limit the tilting movement of the lever around its longitudinal axis without inhibiting the tilting movement around its transverse axis. In this way--upon failure of one brake circuit and the thereby incurred retreat of the associated brake piston--the control lever is permitted to follow this movement only to a small degree so that it does not exert any force on the control piston of the failed circuit. Thus, the remaining, still intact control piston is now acted upon by double the amount of control force with the load on the control lever not having changed, thereby increasing the changeover point of this intact brake circuit correspondingly.